n. 1 a strip of wood or stone forming the bottom of a doorway and crossed in entering a house or room etc. 2 a point of entry or beginning (on the threshold of a new century). 3 Physiol. & Psychol. a limit below which a stimulus causes no reaction (pain threshold). 4 Physics a limit below which no reaction occurs, esp. a minimum dose of radiation producing a specified effect. 5 (often attrib.) a step in a scale of wages or taxation, usu. operative in specified conditions.
[ OE therscold, threscold, etc., rel. to THRASH in the sense 'tread' ]